#include<stdio.h>
   long long int i, j,  N, phi[1000001], k, suma;
  int main()
{

freopen("fractii.in", "r", stdin);
freopen("fractii.out", "w", stdout);
scanf("%lld", &N);

for ( i=1;i<=N;i++)
  phi[i]=i;

for ( i=2;i<=N;i++)
   if (phi[i]==i)
      for (j=i;j<=N;j+=i)
	 phi[j] /=i, phi[j] *= (i-1);

for(k=2;k<=N;k++)
  suma=suma+phi[k];

printf("%lld", 2*suma+1);






return 0;
}